Flow battery control system for a locomotive

ABSTRACT

A flow battery system may include at least one electrolyte tank for storing electrolytes. The system may also include a plurality of reaction cells, each having an output current. The system may further include a plurality of pumps, each associated with one of the plurality of reaction cells, for pumping the electrolytes into the reaction cell at a flow rate. The system may also include a pump sensor configured to monitor the flow rate of at least one of the plurality of pumps. The system may also include an output sensor configured to monitor an output current of at least one of the plurality of reaction cells. The system may further include a controller configured to control the flow rate of at least one of the plurality of pumps based on the output current of the reaction cell associated with the at least one of the plurality of pumps.

TECHNICAL FIELD

This disclosure relates generally to flow batteries and, morespecifically, to a control system for flow batteries in a locomotive.

BACKGROUND

As a result of rising fuel costs and emissions concerns, thetransportation industries are looking for cost-efficient andenvironmentally friendly alternatives for powering vehicles. Inparticular, this has resulted in the development of electrically poweredlocomotives, including hybrid and electric locomotives.

Traditional locomotives are typically powered by diesel electric enginesin which a diesel motor drives an electric generator that produces powerto drive the traction motors and other locomotive systems. The use of alocomotive energy system that is further able to capture energygenerated by the traction motors during regenerative braking is onesolution for increasing the efficiency of the locomotive. For example,batteries may be used to capture and provide energy for hybridlocomotives. For batteries to provide a feasible solution to the energyrequirements of locomotives, a practical method of controlling andimplementing these systems under the size and weight constraints of alocomotive is desirable.

One solution for energy management of hybrid locomotives is described inU.S. Pat. No. 6,591,758 B2 (“the '758 patent”). The '758 patent isdirected to a hybrid energy locomotive system having an energy storageand regeneration system that may purportedly be located in a separateenergy tender vehicle. The energy storage and regeneration systemcaptures dynamic braking energy, excess motor energy, and externallysupplied energy and stores the captured energy in one or more energystorage subsystems, including a flywheel, a battery, an ultra-capacitor,or a combination of such subsystems. The energy storage and regenerationsystem can be located in a separate energy tender vehicle, which isoptionally equipped with traction motors. An energy management system isresponsive to power storage and power transfer parameters, includingdata indicative of present and future track profile information, todetermine present and future electrical energy storage and supplyrequirements. The energy management system controls the storage andregeneration of energy accordingly.

Although the system and method disclosed in the '758 patent may storeand regenerate energy on a locomotive, the system and method disclosedin the '758 patent may still suffer from a number of possible drawbacks.For example, the system and method disclosed in the '758 patent does notincorporate a flow battery system into a locomotive, nor does itdisclose a method of controlling a flow battery system to regulate theoutput current of the reaction cells. Additionally, the '758 patent doesnot disclose a method of powering an auxiliary load when the system isin standby. Therefore, it may be desirable to provide an energydistribution system and method that enables transfer of energy amonglocomotives in a consist.

The presently disclosed systems and methods may mitigate or overcome oneor more of the above-noted drawbacks and/or other problems in the art.

SUMMARY

In one aspect, this disclosure is directed to a flow battery system. Theflow battery system may include at least one electrolyte tank forstoring electrolytes. The system may also include a plurality ofreaction cells, each having an output current. The system may furtherinclude a plurality of pumps, each associated with one of the pluralityof reaction cells, for pumping the electrolytes into the reaction cellat a flow rate. The system may also include a pump sensor configured tomonitor the flow rate of at least one of the plurality of pumps. Thesystem may also include an output sensor configured to monitor an outputcurrent of at least one of the plurality of reaction cells. The systemmay further include a controller configured to control the flow rate ofat least one of the plurality of pumps based on the output current ofthe reaction cell associated with the at least one of the plurality ofpumps.

According to another aspect, this disclosure is directed to a method ofcontrolling the electrical output of a flow battery system. The flowbattery system may include a plurality of reaction cells, each reactioncell having an output current and a plurality of pumps, each pump havinga flow rate. The method may include monitoring the flow rates associatedwith the plurality of pumps. The method may also include monitoring theoutput currents associated with the reaction cells. The method mayfurther include controlling the flow rate of at least one of theplurality of pumps based on the output current of the reaction cellassociated with the at least one of the plurality of pumps.

In accordance with another aspect, a locomotive may include a pluralityof axles and a plurality of pairs of wheels, each pair of wheelsconnected to one of the plurality of axles. The locomotive may alsoinclude a plurality of traction motors, each traction motor rotatablycoupled to one of the axles. The locomotive may further include a flowbattery system configured to at least partially power the plurality oftraction motors. The flow battery system may include at least oneelectrolyte tank for storing electrolytes. The flow battery system mayalso include a plurality of reaction cells, each having an outputcurrent. The flow battery system may further include a plurality ofpumps, each associated with one of the plurality of reaction cells,configured to pump the electrolytes into the one of the plurality ofreaction cells at a flow rate. The flow battery system may also includea pump sensor configured to monitor the flow rate of at least one of theplurality of pumps and an output sensor configured to monitor an outputcurrent of at least one of the plurality of reaction cells. The flowbattery system may further include a controller configured to controlthe flow rate of at least one of the plurality of pumps based on theoutput current of the at least one of the plurality of reaction cellsassociated with the at least one of the plurality of pumps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary embodiment of a locomotive.

FIG. 2 is a block diagram of an exemplary embodiment of an energydistribution system.

FIG. 3 is a flow diagram depicting an exemplary embodiment of a methodof controlling a flow battery system.

DETAILED DESCRIPTION

FIG. 1 shows a perspective view of an exemplary embodiment of alocomotive 100 in which systems and methods for energy distribution maybe implemented consistent with the disclosed embodiments. Locomotive 100may be any electrically powered rail vehicle employing traction motorsfor propulsion. Furthermore, any electrically powered vehicle could alsoincorporate the systems and methods for energy distribution consistentwith the disclosed embodiments.

According to the exemplary embodiment illustrated in FIG. 1, locomotive100 may include a plurality of pairs of wheels 110, with each pair ofwheels 110 connected to an axle 120. Each axle 120 may be rotatablycoupled to a traction motor 130 that is configured to provide force forpropelling locomotive 100. Locomotive 100 may also include an energydistribution system 140 configured to at least partially power theplurality of traction motors 130 of locomotive 100. For example, whenone or more of traction motors 130 supplies force for propellinglocomotive 100, traction motors 130 provide a load on energydistribution system 140 (see FIG. 2). According to some embodiments, oneor more of traction motors 130 may be configured to operate as electricgenerators, for example, when traction motors 130 act to reduce thespeed of locomotive 100, for example, via regenerative braking.According to such embodiments, when traction motors 130 act to reducethe speed of locomotive 100, some embodiments of energy distributionsystem 140 may be configured to store and/or divert energy supplied bytraction motors 130 for use at a later time and/or by other parts oflocomotive 100 (e.g., other traction motors 130).

FIG. 2 is a block diagram of an exemplary embodiment of an energydistribution system 140. As shown in FIG. 2, exemplary energydistribution system 140 may include a flow battery system 200. Exemplaryflow battery system 200 shown in FIG. 2 is configured for use with aload 210 and an auxiliary load 215. For example, load 210 may representthe loads on energy distribution system 140 when traction motors 130operate to propel locomotive 100. Auxiliary loads 215 may represent theloads on energy distribution system 140 from other systems (not shown),such as controllers that operate locomotive 100. Exemplary energydistribution system 140 shown in FIG. 2 is configured for use with oneload 210 and one auxiliary load 215, but it is contemplated that theexemplary energy distribution system 140 can accommodate more loads 210and/or auxiliary loads 215.

As shown in FIG. 2, exemplary flow battery system 200 may include aplurality of reaction cells 220. The exemplary system shown in FIG. 2includes two reaction cells 220, but flow battery system 200 can bemodified to include more reaction cells 220. Each reaction cell 220 mayinclude two half-cells 221 and 222 separated by a membrane 223. Flowbattery system 200 may operate to provide energy by a chemical reactioncaused by two electrolytes. For example, the two electrolytes, which actas energy carriers, may each be delivered into one of the two half-cells221 and 222. For example, half-cell 221 may receive positively chargedelectrolytes, and half-cell 222 may receive negatively chargedelectrolytes. Membrane 223 may prevent the two electrolytes from mixingwith one another, but may allow selected ions to pass through tocomplete a reduction-oxidation (“redox”) reaction, which causeselectricity to flow through reaction cell 220, thereby creating avoltage difference between a pair of electrodes 224 and 225 associatedwith reaction cell 220.

In the exemplary embodiment shown in FIG. 2, to deliver power to load210 and/or auxiliary load 215, the chemical energy contained in theelectrolytes may be released in a reverse reaction, and electricalenergy can be drawn from electrodes 224 and 225. FIG. 2 shows load 210and auxiliary load 215 electrically connected to electrodes 224 and 225to receive power from reaction cell 220. To charge the electrolytes,energy distribution system 140 may supply electrical energy tohalf-cells 221 and 222, which may cause a chemical reduction reaction inone electrolyte mixture and an oxidation reaction in the other. Forexample, FIG. 2 shows load 210 and auxiliary load 215 that may operateas energy sources, such as generators, providing power to chargeelectrolytes in half-cells 221 and 222 of reaction cells 220. Accordingto some embodiments, one or more of exemplary traction motors 130 shownin FIG. 1 may be able to operate as both an electrical load and as agenerator.

The electrolytes may contain one or more dissolved electroactivespecies. The two electrolytes may include positively chargedelectrolytes and negatively charged electrolytes. For example, theelectrolytes may include vanadium ions in different oxidation states.Alternatively, the electrolytes may include polysulfide bromide,uranium, zinc-cerium, or zinc-bromide. There are a variety of otherchemical compounds and combinations known in the art that are capable ofacting as electroactive species, and it is contemplated that theelectrolytes used in exemplary flow battery system 200 may include oneor more of those compounds and combinations.

Exemplary flow battery system 200 may include an electrolyte tank forstoring electrolytes. For example, flow battery system 200 in FIG. 2includes two electrolyte tanks 230 and 240. Electrolyte tanks 230 and240 may be located separately from reaction cell 220 and may beconfigured to deliver the stored electrolytes to reaction cell 220. Forexample, first electrolyte tank 230 may store positively chargedelectrolytes and second electrolyte tank 240 may store negativelycharged electrolytes. In some embodiments, first electrolyte tank 230may store cathode electrolytes (“catholytes”) and second electrolytetank 240 may store anode electrolytes (“anolytes”). In thisconfiguration, first electrolyte tank 230 may provide positively chargedelectrolytes to half-cell 221, and second electrolyte tank 240 mayprovide negatively charged electrolytes to half-cell 222.

According to some embodiments, first electrolyte tank 230 may beconfigured to provide positively charged electrolytes to a plurality ofhalf-cells 221. Similarly, second electrolyte tank 240 may be configuredto provide negatively charged electrolytes to a plurality of half-cells222. In this manner, electrolyte tanks 230 and 240 may supplyelectrolytes to multiple reaction cells 220 to power one or more loads210 and/or auxiliary loads 215. Likewise, electrolyte tanks 230 and 240may supply electrolytes to multiple reaction cells 220 to chargeelectrolytes from one or more loads 210 and/or auxiliary loads 215operating as power sources, such as during regenerative braking.

According to some embodiments, first electrolyte tank 230 may beconfigured to provide positively charged electrolytes to only onehalf-cell 221. Similarly, second electrolyte tanks 240 may be configuredto provide negatively charged electrolytes to only one half-cell 222. Inthis configuration, each pair of electrolyte tanks 230 and 240 maysupply electrolytes to a single reaction cell 220 to power one or moreloads 210 and/or auxiliary loads 215.

According to some embodiments, one or more of electrolyte tanks 230 and240 may be configured to store both charged and uncharged electrolytes.For example, first electrolyte tank 230 may include a first tankseparator 232 to prevent charged electrolytes from mixing with unchargedelectrolytes. In a similar manner, second electrolyte tank 240 mayinclude a second tank separator 242. For example, in FIG. 2, chargedelectrolytes may be stored in a tank portion 234 of electrolyte tank230, and discharged electrolytes may be stored in a tank portion 236 ofelectrolyte tank 230. Similarly, charged electrolytes may be stored in atank portion 244 of electrolyte tank 240, and discharged electrolytesmay be stored in a tank portion 246 of electrolyte tank 240. In someembodiments, the relative charge of the electrolytes stored in portions234, 236, 244, and 246 of electrolyte tanks 230 and 240 varies duringoperation of energy distribution system 140. That is, portion 234 and244 may start out storing discharged electrolytes, but through thecourse of operation, portions 234 and 244 may store electrolytes thathave been charged via, for example, regenerative braking of tractionmotors 130.

Tank separators 232 and 242 may be movable and able to travel withinelectrolyte tanks 230 and 240, respectively, to account for changingvolumes of charged and discharged electrolytes as flow battery system200 operates to charge or discharge the electrolytes. According to someembodiments, tank separators 232 and 242 may be buoyant. Alternativelyor additionally, tank separators 232 and 242 may include flow passagesthat may be selectively opened and closed to allow electrolytes totravel through separator to the other side of electrolyte tank 230 and240 for mixing. Other configurations of tank separators 232 and 242 willbe apparent.

As shown in FIG. 2, exemplary flow battery system 200 may also include aplurality of pairs of pumps 250 and 255. For example, each pair of pumps250 and 255 may be associated with at least one reaction cell 220. Pumps250 and 255 may be configured to pump electrolytes between electrolytetanks 230 and 240 and reaction cell 220 through conduits 260. Forexample, first pump 250 may pump negatively charged electrolytes fromelectrolyte tank 240 through conduit 260 into half-cell 222 of reactioncell 220. In a similar manner, second pump 255 may pump positivelycharged electrolytes from electrolyte tank 230 through conduit 260 intohalf-cell 221 of reaction cell 220.

Exemplary flow battery system 200 may include a controller 270 tocontrol the operation of pumps 250 and 255. According to someembodiments, controller 270 may be configured to change the flow ratesof one or more pumps 250 and 255. Additionally, or alternatively,controller 270 may also be configured to receive signals indicative ofthe real-time status of flow battery system 200 and/or the components ofthe system. For example, controller 270 may receive signalsrepresentative of the flow rates of each of pumps 250 and 255 and theoutput currents of each of reaction cells 220. Controller 270 may embodya single microprocessor or multiple microprocessors that include a meansfor controlling the operation of pumps 250 and 255 and for communicatingwith load 210 and auxiliary load 215. Numerous commercially availablemicroprocessors can be configured to perform the functions of controller270. It should be appreciated controller 270 could readily embody ageneral machine or engine microprocessor capable of controlling numerousmachine or engine functions. Controller 270 may include all thecomponents required to run an application such as, for example, amemory, a secondary storage device, and a processor, such as a centralprocessing unit or any other means known. Various other known circuitsmay be associated with controller 270, including power source circuitry(not shown) and other appropriate circuitry.

According to some embodiments, controller 270 may be configured tocontrol the operation of one or more of pump 250 and 255 based on, forexample, the power needs of one or more of loads 210 and/or auxiliaryloads 215. The power requirements of loads 210 and auxiliary loads 215may be understood in terms of electrical energy, and a correlation mayexist between the electrical energy that reaction cells 220 may supplythrough electrodes 224 and 225 and the flow rates of one or more ofpumps 250 and 255. This correlation may depend on a variety of factors,such as, for example, the average fluid energy density or the averageelectrode power density of the electrolytes. Other environmental factorsmay also affect this correlation, such as the temperature of flowbattery system 200 and/or the capacity of pumps 250 and 255.

According to some embodiments, controller 270 may receive sensor datafrom a variety of sensors. For example, a plurality of sensors 280 (e.g.pump sensors) may be configured to provide signals to controller 270indicative of the flow rate of electrolytes through conduits 260associated with one of pumps 250 and 255. Additionally, oralternatively, flow battery system 200 may include a plurality ofsensors 290 (e.g. output sensors) configured to monitor and to providesignals to controller 270 indicative of the output current of at leastone of reaction cells 220. In some embodiments, sensors 290 may beconfigured to monitor and provide signals to controller 270 indicativeof the output current or voltage of at least one of reaction cells 220.

According to some embodiments, controller 270 may be configured toreceive signals indicative of the magnitude of output current and/oroutput voltage supplied by one or more of reaction cells 220, andcontrol the operation of one or more of pumps 250 and 255 based on thosesignals. Based on the information that controller 270 receives from thesensors, controller 270 may be configured to increase the flow rate ofat least one of pumps 250 and 255 associated with reaction cell 220having an output current that is lower than at least one of the outputcurrents of other reaction cells 220. Additionally, or alternatively,based on the information that controller 270 receives from the sensors,controller 270 may be configured to control the flow rates of pumps 250and 255 to maintain a desired voltage level for reach of reaction cells220 and/or to maintain the same output current for each of reactioncells 220.

According to some embodiments, controller 270 may be configured toreceive signals indicative of the operation mode of flow battery system200. Additionally, or alternatively, controller 270 may be configured toreceive signals indicative of a request to power particular loads 210and/or auxiliary loads 215. For example, controller 270 may beconfigured to identify when flow battery system 200 is in a standby modeand to receive a request to power auxiliary load 215 during the standbymode. Controller 270 may selectively operate at least one of reactioncells 220 to provide power to auxiliary load 215, based on the requestto power auxiliary load 215. In selectively operating at least one ofreaction cells 220, controller 270 may choose which reaction cell 220 tooperate based on the output voltages of each of reaction cells 220.Additionally, or alternatively, controller 270 may choose which reactioncell 220 to selectively operate based on which reaction cells 220 havebeen previously selectively operated in the standby mode.

According to some embodiments, the control of pumps 250 and 255 maydepend on the configuration of flow battery system 200. For example, inembodiments in which each reaction cell 220 is associated with aseparate load, controller 270 may be configured to control the flowrates of pumps 250 and 255 based on the electrical requirements of theseparate loads. For example, in embodiments in which reaction cells 220are connected in parallel to one another, controller 270 may beconfigured to control the flow rates of pumps 250 and 255 to maintainthe same output current from each of reaction cells 220.

FIG. 3 is a flow diagram depicting an exemplary method of controllingflow battery system 200. At step 300, controller 270 may receive one ormore signals indicative of the flow rates of each of pumps 250 and 255,and at step 310, controller 270 may monitor the flow rates of each ofpumps 250 and 255. At step 320 controller 270 may receive one or moresignals indicative of the output currents associated with each ofreaction cells 220. At step 330, controller 270 may monitor the outputcurrents associated with each of reaction cells 220.

At step 340, controller 270 may control the flow rate of at least one ofpumps 250 and 255 based on the output current of the reaction cellassociated with the at least one of pumps 250 and 255. According to someembodiments, controlling the flow rates of at least one of pumps 250 and255 may include maintaining a desired voltage output for each ofreaction cells 220. Additionally, or alternatively, controlling the flowrates may include maintaining the same output current from each ofreaction cells 220.

According to some embodiments, the method may also include determiningan electrical requirement of a load associated with at least onereaction cell 220. For example, controller 270 may receive these signalsindicative of the electrical requirement from sensors, such as outputsensors 290, or from the load itself. In some embodiments, the signalsindicative of the electrical requirements of loads 210 and/or auxiliaryloads 215 may be indicative of operator commands (e.g., via an operatorinput device for controlling the output of loads 210 and/or auxiliaryloads 215). The method may also include controlling the flow rates of atleast one pump 250 and 255 based on the electrical requirement of load210 and/or auxiliary load 215. For example, controlling the flow ratesbased on the electrical requirements of load 210 and/or auxiliary load215 may include providing a sufficient flow of electrolytes to areaction cell 220 associated with the load and/or auxiliary load to meetthe desired output.

INDUSTRIAL APPLICABILITY

The disclosed systems and methods may provide a robust solution forelectric locomotive tractive powering. By allowing dynamic control offlow batteries in both discharging and charging modes, the systems andmethods described herein may result in locomotives powered at leastpartially by battery being a viable alternative to locomotives poweredprimarily by fossil fuels. As a result, operating costs associated withlocomotives may be significantly reduced and more predictable as theymay be less reliant on changing (and increasing) fossil fuel costs.

The disclosed systems and methods may provide several advantages. Forexample, selectively operating particular reaction cells to power anauxiliary load when the flow battery system is in standby mode mayincrease the working life of the reaction cells. A reaction cell mayhave a finite number of charge cycles during its lifetime, and balancingthe charge cycles of all the reaction cells in a system may decrease thetime spent replacing reaction cells.

Additionally, controlling the flow rate of pumps may provide a method ofincreasing the efficiency of locomotives as the power provided to eachof the loads can be more precisely controlled. For example, the flowrate of pumps may be adjusted to account for changes in conditions thataffect the electrical output of the reaction cells.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the exemplary flow batterycontrol system. Other embodiments of the present disclosure may beapparent to those skilled in the art from consideration of thespecification and practice of the present disclosure. It is intendedthat the specification and examples be considered as exemplary only,with a true scope of the present disclosure being indicated by thefollowing claims and their equivalents.

1-16. (canceled)
 17. A locomotive, comprising: a plurality of axles; aplurality of pairs of wheels, each pair of wheels connected to one ofthe plurality of axles; a plurality of traction motors, each tractionmotor rotatably coupled to one of the axles; and a flow battery systemconfigured to at least partially power the plurality of traction motors,the flow battery system comprising: at least one electrolyte tank forstoring electrolytes; a plurality of reaction cells, each having anoutput current; a plurality of pumps, each associated with one of theplurality of reaction cells, configured to pump the electrolytes intothe one of the plurality of reaction cells at a flow rate; a pump sensorconfigured to monitor the flow rate of at least one of the plurality ofpumps; an output sensor configured to monitor an output current of atleast one of the plurality of reaction cells; and a controllerconfigured to control the flow rate of at least one of the plurality ofpumps based on the output current of the at least one of the pluralityof reaction cells associated with the at least one of the plurality ofpumps.
 18. The locomotive of claim 17, wherein the output current ofeach of the plurality of reaction cells is the same and the reactioncells are connected in parallel to one another.
 19. The locomotive ofclaim 18, wherein the controller is configured to further control theflow rates of the plurality of pumps to maintain a desired voltageoutput for each of the reaction cells.
 20. The locomotive of claim 18,wherein the controller is further configured to: identify when the flowbattery system is in a standby mode; receive a request to power anauxiliary load during the standby mode; and selectively operate at leastone of the plurality of reaction cells to provide power to the auxiliaryload in the standby mode.